A turbo blower is a machine, which suctions and blows external air by rotating an impeller at a high speed using torque of a motor, and is used for transfer of powder or aeration at a sewage plant etc.
According to such a turbo blower, rotation of the motor does not reach a steady state in the early operation and the pressure of the blown air is correspondingly low, so it is difficult to achieve the original objects such as aeration when using the turbo blower at a sewage plant.
Accordingly, the motor is made to quickly reach the steady state by discharging the blown air to the atmosphere until the torque of the motor reaches the steady state, and then, the air is blown to the originally desired location.
For this purpose, a butterfly valve is used in the related art, in which an actuator operates a valve using high-pressure air produced by a compressor, thereby discharging air blown in the early operation of a turbo blower, and then the air is blown to the originally desired location when a steady state is entered.
However, in this case, a lot of electricity is wasted because a separate compressor should be operated to produce high-pressure compressed air, and air may not be discharged due to some trouble with the compressor, which may cause a problem with the operation of the turbo blower. Further, a tube connecting the compressor and the butterfly valve to each other occupies a space, so it is troublesome. Further, a lot of troubles are caused by the length of the tube and a separate power for operating the compressor.
A blow-off valve has been developed to solve these problems.
The blow-off valve prevents a compression part of a turbo blower entering surge by discharging pressurized air remaining in a discharge pipe to the outside when the operation of the turbo blower is not in a steady state such as the early stage or stop of operation.
A conventional blow-off valve has been disclosed in Korean Patent No. 861248. This blow-off valve is configured to be operated by pressurized air from a turbo blower.
The blow-off valve requires a spool valve that is moved up and down to blow air. The spool valve includes a vertical shaft (stem) and a valve seat (second spool) that opens/closes an air channel at a lower end.
A rubber diaphragm is disposed over the shaft, so the diaphragm is repeatedly compressed to a valve cover (head) and returned to the initial position in the process of blowing air.
However, the structure of the blow-off valve is complicated, so the process of manufacturing and providing a complete product is complicated and the manufacturing process takes a lot of time.
Therefore, a BOV valve that uses differential pressure and can be accurately operated even without a complicated structure has been proposed.